DCC Bus Terminator/Filter/Snubber Wiring Diagram

Just a really quick post…

Someone asked me recently about DCC bus terminators (or, more accurately, ‘filters’ or ‘snubbers’), whether you should use them and, if so, how to wire them. So, I knocked up a quick diagram for them and I’ve uploaded it to the website in case it’s of use to others. It’s a very simple circuit!

There are different schools of thought on whether a terminator/filter/snubber is required. My own take is that for most small to medium layouts, they’re probably not necessary as a default. However, for bigger layouts or if you’re having reliability issues/unexpected performance problems, it’s probably worthwhile installing them.

If your DCC bus is a loop, then no filter is required (it’s also moot whether this is a good way to do it or not). If it’s a single run, then you only need a single filter at the end. If you’ve got for a T-shaped bus or you have more than one bus, then you’ll need a filter for the end of each run. Simples!

Note: Some people have reported conflicts and false positives with block/occupancy detection when a filter is installed – it’s something to be aware of. It perhaps also goes without saying, but remember that if you’re using block or occupancy detection technology, the filter should be installed on the end of the DCC bus and not on a leg from the detector module.